Effects of Fruit Thinning on Fruit Sugar Accumulation and Leaf Photosynthetic Characteristics of Pear Effects of Fruit Thinning on Fruit Sugar Accumulation and Leaf Photosynthetic Characteristics of Pear Studies on individual sexual reproductive process of Juglans mandshurica Effect of topping and fruit thinning on translocation and distribution of foliar 15N-urea at fruit inflating stage of nectarine under greenhouse condition